1. Field of the Invention
The invention relates to radio frequency identification (RFID) technology, and in particular, to verifying RFID tags singulated by RFID readers.
2. Background Art
Radio frequency identification (RFID) tags are electronic devices that may be affixed to items whose presence is to be detected and/or monitored. The presence of an RFID tag, and therefore the presence of the item to which the tag is affixed, may be checked and monitored wirelessly by devices known as “readers.” Readers typically have one or more antennas transmitting radio frequency signals to which tags respond. Because the reader “interrogates” RFID tags, and receives signals back from the tags in response to the interrogation, the reader is sometimes termed as “reader interrogator” or simply “interrogator.”
With the maturation of RFID technology, efficient communication between tags and interrogators has become a key enabler in supply chain management, especially in manufacturing, shipping, and retail industries, as well as in building security installations, healthcare facilities, libraries, airports, warehouses, etc.
In a relatively dense reader environment, the possibility exists that a signal from a RFID tag will be sensed not only by the nearby reader powering the tag, but also by a second reader that is physically positioned far away from the tag. Although the second reader does not power the tag, it still may be able to receive a response from the tag. This phenomenon is called a “cross-read” of the tag, where a reader reads a tag located outside a range of its transmitter. Such cross-reads are undesirable in certain situations. For example, if the second reader reads the tag being powered by the first reader, the determined location of the tag may be incorrect.
Cross-read events can be mitigated by implementing a proper physical layout of RFID system components, and by proper configuration of RF parameters. However, despite this, some non-negligible cross-reads tend to occur over time.
Thus, what is needed are ways to improve a quality of communications between readers and tags in an RFID communications environment, such as a warehouse environment, to improve tag read rates and to avoid cross-reads of tags.